Combustion of stratified mixtures in a constant volume chamber

The combustion of lean propane/air and methane/air stratified mixtures in a constant volume chamber was investigated, focusing on the influence of stratification, overall equivalence ratio, and delay between injection and ignition. The gaseous fuel was injected in a parallelepipedic chamber (120*70*58 mm³) previously filled with air at 1 bar and 293 K. A comparison was made for the combustion of three mixtures (overall equivalence ratio φ_oa = 0.8:1), i.e., homogeneous mixture initially at rest in the chamber; injection of an amount of 0.8:1 mixture in the chamber initially filled with the same mixture; and injection of a pure fuel in the chamber initially filled with air to obtain φ_oa = 0.8:1. Reservoir pressure and injection duration were the same for the last two cases. For methane, the highest combustion velocity was obtained by the turbulent homogeneous mixture, and the lowest velocity by the initially quiescent homogeneous mixture. For propane, the lowest value of combustion velocity was obtained by the stratified mixture.